Having demonstrated that fat cell plasma membrane functions (hormone-sensitivity of adenylate cyclase, insulin binding and a glucose transport) are all decreased after 5 days of feeding a high fat diet, carbohydrate free diet we propose to study the effects of fat feeding on the chemical morphology of the plasma membrane and on the synthesis of membrane components. Since preliminary experiments with concanavalin A revealed a decreased inhibition of insulin binding by the lectin in cells of fat diet-adapted rats we propose to compare the binding of concanavalin A and other lectins to fat cells of such animals. We also intend to make systematic comparisons of glycoprotein sugar composition, incorporation of precursor sugars into membrane glycoproteins, lipid composition of membranes and turnover of individual membrane constituents in rats adapted to high fat and carbohydrate diets. Since insulin insensitivity and diminished insulin binding have been described after fructose (versus glucose) feeding we will perform parallel experiments on rats adapted to fructose diets.